JUBA/ADDIS ABABA, March 5 (Reuters) - At least five soldiers were killed in fighting between soldiers over delayed salaries at a barracks in South Sudan's capital on Wednesday, an army spokesman said, three months after clashes in the same military base triggered a broader conflict.

The spokesman said the situation at the base in Juba was now under control.

The latest flare-up did not appear to be between government and rebel forces, but it highlights tension that persists in the army in Africa's newest nation that came close to civil war before a Jan. 23 ceasefire that has proved shaky.

Regional African bloc IGAD has been trying to mediate but a new round of peace talks has yet to start in earnest. A top mediator said IGAD was aiming to send a contingent of troops to South Sudan to enforce the ceasefire and protect vital oil fields, after crude output fell by a third due to the conflict.

Uganda has raised alarm in the West for sending troops into South Sudan to assist the government of President Salva Kiir, who is battling forces loyal to his sacked deputy president, Riek Machar, who commands his forces from the bush.

Spokesman for the governemnt SPLA army Malak Ayuen said Wednesday's clashes erupted between body guards of commando commander Gatwech Gai, one of the few Nuer senior officers not to defect to Machar, also an ethnic Nuer. Kiir is a Dinka.

He said at least five soldiers were killed in the fighting that was sparked by some soldiers "asking from their commander why their salaries had been delayed".

"We are in a crisis, it was something beyond our control and that is why the salaries were going out now," Ayuen said. "The situation is now under control."

Several of South Sudan's neighbours worry about turning the conflict into a regional tussle, and are frustrated by the continued violations of the ceasefire.

GUNFIRE, BILLOWS OF SMOKE

Wednesday's fighting was in the same barracks where clashes erupted in mid-December and led to a broader conflict that has killed thousands and driven more than 800,000 people from their homes. The conflict has re-opened deep ethnic faultlines.

Gunfire sent people in Juba scurrying through the streets for safety. Smoke billowed out of the barracks, which the spokesman said was caused by stores hit during the fighting.

IGAD is discussing a "protection and stabilisation force" with the African Union and United Nations to monitor the cessation of hostilities and protect oil fields, officials said.

"The parties would be tempted to fight for control of these resources and if this is protected by this force then definitely it will further stabilise the situation in South Sudan," Seyoum Mesfin, IGAD's chief mediator, told a news conference.

Both sides have accused the other of breaking the truce. The worst fighting since the ceasefire was in Malakal, the capital of South Sudan's main oil producing Upper Nile State.

Overall oil output has fallen to 160,000 barrels per day from about 245,000 bpd before the conflict flared in December.

Seyoum said Ethiopia, Djibouti, Kenya, Rwanda and Burundi were ready to contribute troops to the force, whose size and mandate would be determined at a meeting in Addis Ababa of regional heads of state within the next two weeks.

Officials said it could involve sending a "small contingent" of about 2,000 troops.

"We want to make it cost effective and affordable for the international community to sustain this mission," Seyoum said, adding other standby forces could be sent if violence persisted.

IGAD-sponsored talks are due to resume on March 20 after delays over rebel demands for the freeing of four detainees who rebels say are political prisoners but the government calls coup plotters. (Writing by Aaron Maasho and Richard Lough; Editing by Edmund Blair and Ralph Boulton)